7A12: Difference between revisions

7A12 (view source)

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 The 7A12 was designed by [[Roy Hayes]] (who also designed the [[3A3]] and [[3A8]] before leaving for HP Loveland in Jan 1971).
 The Evaluation Engineer for the 7A12 was [[Peter Starič]], co-author of the book "Wideband Amplifiers" with Erik Margan.
+There were two mistakes, concept errors, that doomed the 7A12 from day 1.  The first was in deciding to use the Tektronix IC process (the "Standard Process") for the signal path.  This process had an Ft of only 1GHz, too slow for a plugin expected to provide 150MHz bandwidth in the fastest mainframe, the 7704.
+The second day 1 mistake, later pointed out by Tom Rousseau, was to arrange the two channels vertically.  Roy wanted to be able to go from one sensitivity (deflection factor) to another without having to go through all the sensitivities in between as happens with a rotary switch.  The non-obvious problem with this is that the two channels, each on its own circuit board, would not be two identical boards.  The boards would be mirror images!  That is far more expensive.
+Tom Rousseau was later tapped to design a new dual trace plugin that had adequate bandwidth and be less expensive to manufacture.  Tom had the advantage of a later, faster IC process.  He chose the M84 (155-0078-xx), already in production for the 485.
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